Why use this instead of underscore.uniq[ue]? A few reasons: * This library updates the array in place without making an extra copy (and so it is faster for large arrays) * It also accepts a custom comparison function so you can remove duplicates from arrays containing object * It is more modular in the sense that it doesn't come with a bazillion other utility grab bag functions.

Node.js is an event-based server-side JavaScript engine.